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Thread: New Water Heater, low pressure

  1. #1

    Default New Water Heater, low pressure

    I live in a 2 full bath condo. My water heater which was 19 years old just broke due to a shelf falling on the drain pipe and bursting it. Prior to this accident, the water heater was great. I could use the dishwasher and shower, toilet and shower, even washing machine and shower without losing hot water OR even a decrease in water pressure. Now, I just got my new energy efficient water heater, and if the shower is on and I flush the toilet, the shower pressure cuts in 1/2. What's up with that?? Both water heaters were 40 gallons. Is there anything to check in terms of pipers, or anything that can be done??? Or is the old one just built better?


  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default heater

    The only thing in the new heater that could cause a pressure drop would be the heat trap fittings on the inlet and outlet, assuming yours even has them. But if the problem is in the water heater, it should not be affected by flushing a toilet which uses the cold water system.

  3. #3


    Well, I'm not assuming its the water heater, but the problem just started happening when the new water heater was installed. I made sure my two water in pipe valves were open (the 2 on either side of the meter). Is there anything else that I may be missing?

  4. #4
    DIY Junior Member mrjetskey's Avatar
    Join Date
    Apr 2005


    Its possible that when the old heater was broken pieces of calcium and other minerals could have found there way into your water line then get caught at the outlet especially if you have the single handle units that use cartridges.I found 3 of ours plugged after our water company installed new tap for house next door.It doesnt take a very large piece of mineral to plug one of the new cartridges.That would explain the hot and cold both having pressure drop, OR it could be they didnt open up the cold water supply line for the house completely,or the 90 degree valves the water company uses might be 1/2 opened after replacing the hot water heater.Those are all I can think of now hope this helps.


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